Vacuum processing apparatus

ABSTRACT

An object of the disclosure is to provide a vacuum processing apparatus capable of minimizing the size of the whole apparatus by reducing a floor area occupied by a vacuum pump. An etching apparatus  20  for applying an etching process on an object to be processed in a vacuum includes a processing vessel  21  for applying the etching process on a semiconductor wafer W introduced into the vessel  21  and a vacuum pump  30  arranged below the processing vessel  21  so as to be coaxial with the processing vessel  21 , for sucking exhaust gas in the processing vessel  21  to form the vacuum.

BACKGROUND OF THE INVENTION

1. Technical Field of the Invention

The present invention relates to a vacuum processing apparatus in whichan objects to be processed, such as a semiconductor wafer, is processedin a vacuum atmosphere in a semiconductor manufacturing process or thelike.

2. Description of the Related Art

In the semiconductor manufacturing process, the semiconductor wafer isintroduced in a processing vessel capable of forming a vacuum, so thatthe wafer is subjected to film-forming, etching, etc. in the vacuumatmosphere. In such a process in the vacuum atmosphere, aturbo-molecular pump is often used as a vacuum pump for producing thevacuum atmosphere.

As one structure for producing the vacuum atmosphere in the processingvessel by means of the turbo-molecular pump, there is known a plasmaetching apparatus 1 shown in FIGS. 7 and 8. In order to mount a wafer W,the plasma etching apparatus 1 includes a susceptor 3 arranged in aprocessing vessel 2. On the underside of the susceptor 3, a drivingmechanism 4 is provided for driving the susceptor 3 up and down.Further, above the susceptor 3, a shower head 5 is provided forintroducing process gas, such as CF₄, in the processing vessel 2. On thelateral side of the processing vessel 2, for example, two exhaust pipes6 are connected in order to exhaust the vessel 2 thereby to form avacuum therein.

On both sides of the processing apparatus 1, a pair of turbo-molecularpumps 10 are connected with the exhaust pipes 6, respectively. In eachof the turbo-molecular pumps 10, a motor stator 11 is provided for acenter shaft of the pump 10 and a motor rotor 13 is rotatably arrangedabout the motor stator 11 through a bearing 12. The motor rotor 13 isprovided, on its upper portion, with a number of rotors 14 which operateto absorb the process gas downward in the molecular condition. Further,the turbo-molecular pump 10 includes a housing 15 provided with a numberof stators 16.

In operation, when the motor rotors 13 of the turbo-molecular pumps 10are rotated simultaneously, the great number of rotors 14 are alsorotated against the stators 16. Consequently, the exhaust gas in theprocessing vessel 2 is sucked in the molecular condition via the exhaustpipes 6, so that the interior of the processing vessel 2 is maintainedunder a generally vacuum condition.

However, there exists a problem in the above structure where the pair ofturbo-molecular pumps 10 are arranged on both sides of the processingapparatus 1 in order to form a vacuum in the processing vessel 2. Theproblem is that the floor area occupied by the turbo-molecular pumps 10is too large. Therefore, it is apprehended that, with the futureprogress of the large diameter semiconductor wafer, the floor areaoccupied by the vacuum pumps is further increased thereby to cause theprocessing installation to be large-sized. Under such an anticipation,there is an eager demand to reduce the floor space to be occupied by thevacuum pump to the utmost.

SUMMARY OF THE INVENTION

Under such a situation, it is therefore an object of the presentinvention to provide a vacuum processing apparatus which is capable ofminimizing the size of the whole apparatus in order to reduce the floorarea to be occupied by the vacuum pump.

According to the first feature of the invention, there is provided avacuum processing apparatus for applying a designated process on anobject to be processed in a vacuum atmosphere, comprising a processingvessel for applying the designated process on the object introducedthereinto, and a vacuum pump arranged on either downside or upside theprocessing vessel so as to be coaxial with the processing vessel, forsucking exhaust gas in the processing vessel thereby to form a vacuum.In this way, when arranging the vacuum pump on either downside or upsideof the processing vessel coaxially, then it is possible to remarkablyreduce the floor area occupied by the vacuum pump in comparison with acase of arranging the vacuum pump on the lateral side of the processingvessel, whereby the whole processing apparatus can be small-sized.Therefore, even if the processing vessel is caused to be large-sizedwith the future large diameter object to be processed, it is possible toprevent the floor area occupied by the whole apparatus from beingincreased remarkably.

The second feature of the invention resides in that, in the arrangementwhere a susceptor for mounting the object is provided in the processingvessel, the vacuum pump is arranged below the susceptor so as to becoaxial with the processing vessel. In this case, it is possible toreduce the occupied area furthermore.

The third feature of the invention resides in that the vacuum pump isconstructed cylindrically as the whole. In this case, it is possible toreduce the occupied area remarkably.

According to the fourth feature of the invention, there is provided avacuum processing apparatus for applying a designated process on anobject to be processed in a vacuum atmosphere, comprising: a processingvessel for applying the designated process on the object introducedthereinto, the processing vessel being provided, therein, with asusceptor for mounting the object thereon; a vacuum pump constructedcylindrically as a whole and arranged below the susceptor in theprocessing vessel so as to be coaxial with the processing vessel, forsucking exhaust gas in the processing vessel thereby to form a vacuum;and a driving mechanism arranged below the susceptor, for moving it upand down, wherein the vacuum pump is arranged around the drivingmechanism coaxially therewith. In this case, since the vacuum pump isarranged around the large-sized driving mechanism, it is possible toprogress the effect of reducing the occupied floor area remarkably.

The fifth feature of the invention resides in that the vacuum pump is aturbo-molecular pump.

According to the sixth feature of the invention, there is provided avacuum processing apparatus for applying a designated process on anobject to be processed in a vacuum atmosphere, comprising: a processingvessel for applying the designated process on the object introducedthereinto, the processing vessel being provided, therein, with asusceptor for mounting the object thereon; a turbo-molecular vacuum pumpconstructed cylindrically as a whole and arranged below the susceptor inthe processing vessel so as to be coaxial with the processing vessel,for sucking exhaust gas in the processing vessel thereby to form avacuum, the turbo-molecular vacuum pump including: a cylindrical innerhousing arranged in coaxial with the processing vessel; a cylindricalmotor stator arranged outside the cylindrical inner housing; a number ofrotors rotatably arranged with respect to the cylindrical motor stator;a cylindrical outer housing arranged outside the rotors; and a number ofstators fixed to the cylindrical outer housing so as to each extendbetween the adjacent rotors; and a driving mechanism arranged below thesusceptor, for moving it up and down, wherein the vacuum pump isarranged around at least a portion of the driving mechanism coaxiallytherewith. In a conventional motor having a rotating member like arotor, there has been no idea to provide a rotating shaft of therotating member in the form of a cylinder and dispose another mechanismin the shaft.

The seventh feature of the invention resides in that the vacuumprocessing apparatus further comprises an exhaust port communicatingwith the vacuum pump and opening to the interior of the processingvessel, wherein the exhaust port is arranged in a floor of theprocessing vessel annularly and uniformly. The eighth feature of theinvention resides in that the exhaust port is identical to an annularopening succeeding in the circumferential direction of the processingvessel. The ninth feature of the invention resides in that the exhaustport is constituted by a plurality of openings separated from each otherin the circumferential direction of the processing vessel. In this way,owing to the arrangement where the exhaust port is formed in thecircumference of the vessel about the axis, it is possible to performthe exhausting operation uniformly and quickly in comparison with a caseof absorbing the gas through the lateral side of the processing vessel.

The tenth feature of the invention resides in that the exhaust port isarranged around the susceptor for mounting the substrate thereon.

The above and other features and advantages of this invention willbecome apparent, and the invention itself will best be understood, froma study of the following description and appended claims, with referencehad to the attached drawings showing a preferred embodiment of theinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view showing a plasma etching apparatus inaccordance with an embodiment of the present invention;

FIG. 2 is a cross sectional view taken along a line II—II of FIG. 1;

FIG. 3 is a cross sectional view taken along a line III—III of FIG. 1,also showing the profile of an exhaust port;

FIG. 4 is a cross sectional view at a position similar to that of FIG.3, also showing the profile of another exhaust port;

FIG. 5 is a view showing streamlines of exhaust gas in case ofsimulating the exhausting operation of the apparatus shown in FIGS. 1and 2;

FIG. 6 is a view showing the pressure distribution in a processingvessel in case of simulating the exhausting operation of the apparatusshown in FIGS. 1 and 2;

FIG. 7 is a plan view showing the etching apparatus equipped with thepair of turbo-molecular pumps;

FIG. 8 is a sectional view showing the etching apparatus equipped withthe pair of turbo-molecular pumps;

FIG. 9 is a view showing streamlines of exhaust gas in case ofsimulating the exhausting operation of the apparatus shown in FIGS. 7and 8; and

FIG. 10 is a view showing the pressure distribution in the processingvessel in case of simulating the exhausting operation of the apparatusshown in FIGS. 7 and 8.

DESCRIPTION OF THE PREFERRED EMBODIMENT

With reference to drawings, a vacuum processing apparatus in connectionwith embodiments of the invention will be described below.

FIG. 1 is a sectional view of a plasma etching apparatus in accordancewith one embodiment of the present invention, while FIG. 2 is a crosssectional view taken along a line II—II of FIG. 1.

As shown in FIG. 1, the plasma etching apparatus 20 is provided, in aprocessing vessel 21, with a susceptor 22 for mounting a semiconductorwafer W thereon. Underside of the susceptor 22, a driving mechanism 23is arranged for moving the susceptor 22 up and down. Further in thesusceptor 22, a plurality of lift pins 24 are provided for receiving theintroduced wafer W and moving it up and down. Around the drivingmechanism 23, a bellows 25 is arranged to divide the interior of theprocessing vessel 21 into a vacuum space and an atmospheric space.

Arranged in a position opposing the susceptor 22 in an upper part of theprocessing vessel 21 is a shower head 26 which serves to introduce theprocess gas (e.g. CF₄ etc.) into the processing vessel 21. The showerhead 26 has an introductory part 26 a formed to introduce the processgas into the head 26 from a gas source (not shown) and a number of gasejecting holes 26 b formed to open on the underface of the head 26.

A high-frequency power source 29 is connected to the shower head 26through a matching circuit 28. With the high-frequency power supply fromthe power source 29 to the shower head 26, the plasma of process gas isproduced in the processing vessel 2, for applying the etching treatmenton the semiconductor wafer W.

Beside the processing vessel 21, there is provided a gate valve 27through which the semiconductor wafer W is introduced into theprocessing vessel 21 and also discharged therefrom. In case of loadingand unloading the semiconductor wafer W, the susceptor 22 is temporarilylowered to a position on a level with the gate valve 27.

On the underside of the plasma etching apparatus 20, a turbo-molecularpump 30 for sucking the exhaust gas in the processing vessel 21 isarranged in coaxial with the vessel 21 and the susceptor 22. As shown inFIG. 2, the turbo-molecular pump 30 is entirely constituted in the formof a cylinder and also communicated with the interior of the processingvessel 21 through the intermediary of an exhaust port 31 in the vessel21. In detail, the exhaust port 31 is arranged in the floor of thevessel 21 along its annular coaxial portion with the susceptor 22. Note,the exhaust port 31 may be constituted by a single annular port, asshown in FIG. 3. Alternatively, as shown in FIG. 4, it may be replacedwith a plurality of exhaust ports 51 which are disposed along thecircumference of the floor and also separated from each other in thecircumferential direction.

The turbo-molecular pump 30 constructed cylindrically on the wholeincludes an inner housing 32 arranged inward in the radial direction soas to surround the lower portion of the driving mechanism 32. Theturbo-molecular pump 30 further includes an outer housing 33 arrangedoutward in the radial direction.

Additionally, outside the inner housing 32, a cylindrical motor stator34 is fitted to the housing 32. A motor rotor 36 is rotatably providedwith respect to the motor stator 34 through a bearing 35.

The motor rotor 36 is provided, on an upper portion thereof, with anumber of rotors 37 for sucking gas downward in the molecular condition.On the side of the outer housing 33, a number of stators 38 are fixed tothe housing 33 so as to each extend between the adjacent rotors 37.

As shown in FIG. 2, each rotor 37 has a number of fins 37 a formedthereon so as to extend outward in the radial direction. The stator 38provided with a number of fins as well, though they are not shown in thefigures. Accordingly, when the rotors 37 are rotated together with thefins 37 a, they allows the exhaust gas to be absorbed downward in themolecular condition in cooperation with the fins of the stable stators38.

In the above-constructed etching apparatus 20, before starting theplasma etching process, the turbo-molecular pump 30 is driven toevacuate the processing vessel 21 into the high vacuum condition.

Then, the process gas is introduced into the processing vessel 21through the shower head 26 while the high-frequency power is suppliedfrom the high-frequency power source 26 through the matching circuit 28,so that plasma of the process gas is produced in the processing vessel21 for plasma-etching the semiconductor wafer W.

In forming a vacuum, the rotation of the rotor motor 36 in theturbo-molecular pump 30 allows the rotors 37 and the fins 37 in greatnumbers to rotate in cooperation with the stable stators 38, so that theexhaust gas is sucked in the molecular condition in the processingvessel 21 through the exhaust port 21. Thus, the interior of theprocessing vessel 21 is maintained in the vacuum condition.

Thus, in this plasma etching apparatus, the turbo-molecular pump 30 isdisposed in coaxial with the susceptor 22 and the driving mechanism 23,while the driving mechanism 23 is arranged inside the inner housing 32of the turbo-molecular pump 30. Therefore, this arrangement allows thecylindrical turbo-molecular pump 30 to be overlapped with the processingchamber 21 downward in plan view. Thus, it is possible to contour thewhole apparatus in the form of a general column without projecting theturbo-molecular pump 30 from the processing chamber 21. Consequently, itis possible to reduce the floor area to be occupied by the wholeapparatus remarkably, whereby the etching apparatus 20 can besmall-sized entirely.

Note, with the recent large diameter wafer, the processing vessel alsotends to be formed to have a large diameter. In such a case, it ispossible to increase the diameter of the turbo-molecular pump 30,corresponding to the large diameter processing vessel 21. Thus, in theetching apparatus 20, it is possible to maintain its compact andcolumnar configuration with no projection. Further, the larger diameterthe turbo-molecular pump 30 has, the more the circumferential speed ofthe rotor 37 is increased and therefore, it is possible to reduce therevolutions to that increased degree. Thus, it becomes easy to meet theproblems of vibrations etc. accompanied with high-speed rotations of thepump 30, allowing the freedom of design to be expanded and themanufacturing cost to be saved.

It is noted that the turbo-molecular pump 30 communicates with theprocessing vessel 21 through the exhaust port 31 (or the exhaust ports51) in the vessel floor in order to perform the exhausting operation. Inconnection, since the exhaust port 31 (or the exhaust ports 51) isformed along the annular portion of the vessel floor around thesusceptor 22, it is possible to evenly exhaust the gas in the processingvessel 21 in comparison with either case of discharging the gas throughthe lateral side of the vessel 21 or a single small hole formed in thevessel floor. Thus, the uniformity of exhausting can be improved incomparison with the conventional structure. Additionally, the exhaustingefficiency can be improved because of the exhausting area larger thanthat of the conventional structure.

In the conventional case of using some turbo-molecular pumps, it hasbeen required to accord the operating conditions of the respective pumpswith each other in order to maintain the uniformity of exhausting. Onthe contrary, according to the plasma etching apparatus of theembodiment, it is possible to realize the uniformity of exhaustingeasily owing to the single turbo-molecular pump 30.

Next, we describe the comparison results of exhausting uniformity insimulation between the present apparatus of FIGS. 1 and 2 and theconventional apparatus of FIGS. 7 and 8. In the figures, FIG. 5 showsthe exhausting streamlines of the apparatus of FIGS. 1 and 2; FIG. 6shows the pressure distribution in the apparatus of FIGS. 1 and 2; FIG.9 shows the exhausting streamlines of the apparatus of FIGS. 7 and 8;and FIG. 10 shows the pressure distribution in the apparatus of FIGS. 7and 8. In FIGS. 6 and 10, concentric lines about the respective centersdesignate isobars.

By comparing FIG. 5 with FIG. 9, it will be understood that theapparatus of FIGS. 1 and 2 has less disturbance in streamlines than theapparatus of FIGS. 7 and 8. Consequently, it is confirmed that theapparatus of the embodiment has a high exhausting uniformity incomparison with that of the conventional apparatus. Further comparingFIG. 6 with FIG. 10, it is found that the apparatus of FIGS. 1 and 2exhibits a circular pressure distribution, while the conventionalapparatus of FIGS. 7 and 8 has a rectangular pressure distribution. Incomparison with the rectangular pressure distribution of theconventional apparatus, the apparatus of the embodiment is easy toprovide an uniform pressure distribution due to the circular pressuredistribution as the result of uniform exhausting. That is, in case ofcircular pressure distribution, the uniform pressure distribution can beobtained by elevating the susceptor 22. While, in case of non-circularpressure distribution, it is necessary to adjust the processingcondition, for example, dispersion of the gas flows. This means that itis impossible for such a non-circular pressure distribution to obtainthe uniform pressure distribution under an optional processingcondition.

The present invention is not limited to the embodiment described aboveand applicable to modifications and variations of the above embodiment.

For example, although the turbo-molecular pump 30 is arranged under theprocessing vessel 21 so as to be coaxial with the vessel 21 and thesusceptor 22 in the above-mentioned embodiment, the turbo-molecular pump30 may be arranged above the processing vessel 21 coaxially. In such acase, the arrangement of the pump 30 around the matching circuit abovethe vessel 21 would progress an effect of miniaturizing the apparatus.

Additionally, although the turbo-molecular pump 30 is employed as thevacuum pump in the shown embodiment, it goes without saying that otherpumps, for example, diffusion pump, drag pump, sputter-ion pump,cryopump, absorption pump, etc. are applicable to the vacuum pump of theinvention. In common with these cases, it is preferable to construct thepump on use symmetrically about an axis.

Furthermore, although the above-mentioned embodiment is represented bythe etching apparatus, the present invention is not limited to this andalso applicable to other vacuum processing apparatus, such as afilm-forming apparatus. In the above-mentioned embodiment, thesemiconductor wafer is used as an object to be processed. Nevertheless,other substrates, for example, LCD substrates may be used as the objectto be processed.

According to the invention, owing to the arrangement where the vacuumpump is arranged on either downside or upside of the processing vesselcoaxially, it is possible to remarkably reduce the floor area occupiedby the vacuum pump in comparison with the conventional arrangement ofthe vacuum pump on the lateral side of the processing vessel, wherebythe whole processing apparatus can be small-sized. Therefore, even ifthe processing vessel is caused to be large-sized with the future largediameter object to be processed, it is possible to prevent the floorarea occupied by the whole apparatus from being increased remarkably.

Further, the above structure allows the exhaust port communicating withthe vacuum pump to be formed in the vessel floor annularly, whereby itis possible to perform the exhausting operation uniformly and quickly incomparison with the case of absorbing the gas through the lateral sideof the processing vessel.

What is claimed is:
 1. A vacuum processing apparatus for applying a designated process to an object to be processed in a vacuum atmosphere, said apparatus comprising: a processing vessel for applying the designated process to the object introduced thereinto; a susceptor located in the processing vessel for mounting the object thereon; a toroidal shaped vacuum pump including a motor therein for sucking exhaust gas from the processing vessel to form a vacuum in the vessel, the toroidal shaped vacuum pump being arranged below the processing vessel and being coaxial with the susceptor, the toroidal shaped vacuum pump defining a column-shaped space that is surrounded by the vacuum pump and that is located below the susceptor, and a driving mechanism for moving the susceptor up and down, the driving mechanism being arranged below the susceptor and received within the column-shaped space surrounded by the toroidal vacuum pump.
 2. A vacuum processing apparatus as claimed in claim 1, wherein the motor includes a cylindrical motor stator, and a cylindrical motor rotor rotatably arranged outside the cylindrical motor stator, and wherein the toroidal shaped vacuum pump further includes: a cylindrical inner housing arranged coaxially with the susceptor, the cylindrical inner housing surrounding and defining the columned space, the cylindrical inner housing being provided with the cylindrical motor stator thereoutside; a cylindrical outer housing arranged coaxially with the susceptor; a number of pump stators provided inside the cylindrical outer housing; and a number of pump rotors provided outside the cylindrical motor rotor, the number of pump rotors each extending between the adjacent pump stators.
 3. A vacuum processing apparatus as claimed in claim 2, wherein the vacuum pump is a turbo-molecular pump.
 4. A vacuum processing apparatus as claimed in claim 2, further comprising an exhaust port communicating with the vacuum pump and opening to the interior of the processing vessel, wherein the exhaust port is arranged in a floor of the processing vessel annularly and uniformly.
 5. A vacuum processing apparatus as claimed in claim 4, wherein the exhaust port has an annular opening which forms continuously in the circumferential direction of the processing vessel, the vacuum pump further includes an annular inlet which forms continuously in the circumferential direction of the vacuum pump, and the annular opening of the exhaust port is directly connected to the annular inlet of the vacuum pump in all circumferential parts of the annular opening and inlet.
 6. A vacuum processing apparatus as claimed in claim 4, wherein the exhaust port is identical to an annular opening succeeding in the circumferential direction of the processing vessel.
 7. A vacuum processing apparatus as claimed in claim 4, wherein the exhaust port is constituted by a plurality of openings separated from each other in the circumferential direction of the processing vessel.
 8. A vacuum processing apparatus as claimed in claim 4, wherein the exhaust port is arranged around the susceptor for mounting the substrate thereon. 